Image processing devices for calibrating image density are well known in the art. One such image processing device disclosed in Japanese unexamined patent application publication No. 2004-114343 performs operations to measure the densities of samples having known densities, and performs calibration to correct changes in image density properties over time and lot variations based on the results of the density measurements in order to prevent errors in density measurements caused by changes over time and the like.
When printing a test image for calibration based on set printing conditions and acquiring calibration data based on the test image, the conventional image-processing device records the acquired calibration data together with printing conditions for the test image in correlated data. When subsequently printing an image, the image-processing device prompts the operator to set printing conditions and select the calibration data for printing the image. If the operator-specified printing conditions do not match the printing conditions corresponding to the operator-selected calibration data, the image processing device issues a warning to the operator, thereby notifying the operator of this inconsistency. Accordingly, the image-processing device can prevent the operator from unknowingly printing an image using inappropriate calibration data.
In the conventional image processing device described above, test images (hereinafter referred to as “density patches”) are stored in association with printing conditions, such as the density, color, resolution, and the like of the image because dither data used for forming images during printing (data having a prescribed threshold set for each dot used to form the image) differs when printing conditions differ. Accordingly, image densities are calibrated by varying density patches for each printing condition and measuring the densities of the varied density patches. As a consequence, there may be five densities for density patches, four colors for images, and three image resolutions, for example, requiring sixty types (5×4×3) of density patches. As the number of printing conditions increases, the number of density patches used in calibration increases correspondingly, increasing the required capacity for a storage device used to store the density patches.
Further, an increase in the number of density patches used for calibration increases the time required for forming the density patches and measuring the density patches, Hence, the conventional method increases the time required for calibration.